1. Field of the Invention
The present invention relates to communication between a wireless base station apparatus and a mobile wireless terminal apparatus which are accommodated in a network.
2. Description of the Related Art
A mobile communication system such as a cellular system uses various parameters for defining the transmission/reception capability of a terminal to support terminals of various application purposes (e.g., 3GPP (3rd Generation Partnership Project) TS 36.306 V8.2.0 (2008 05)). Combinations of parameters define UE categories. Terminal capabilities (UE capabilities) that define the UE categories include a maximum information transmission rate which is defined on each of the transmitting and receiving sides. A base station transmits/receives signals to/from a plurality of terminals based on their different transmission and reception capabilities. The 3GPP (3rd Generation Partnership Project) TS 36.306 V8.2.0 (2008 05) suggests that a base station should be able to simultaneously connect terminals of different categories.
Recently, an LTE-Advanced (LTE-A) system has been examined, which uses a broadband including a system band that is the receivable bandwidth of a Rel-8 LTE terminal. To operate the Rel-8 LTE terminal using a narrowband in the new system using a broadband, the base station of the new system needs to transmit a signal that is receivable by the Rel-8 LTE terminal as well.
The Rel-8 LTE terminal starts its operation ahead of the new system. It is therefore difficult to change the reception band of the Rel-8 LTE terminal later at the start of the operation of the new system. In addition, the ratio of Rel-8 LTE terminals that exist in the radio zone of one base station to terminals (“LTE-A terminals” hereinafter) that use the broadband there dynamically changes. For this reason, the LTE system that assigns information transmission channels via control channels requires some contrivance on the control channel configuration.
The control channels are transmitted using a common resource. The Rel-8 LTE terminal and the LTE-A terminal perform blind determination and detect control information addressed to them. A downlink physical channel transmitted from the base station multiplexes a physical downlink control channel (PDCCH) and physical downlink shared channel (PDSCH) (e.g., 3GPP TS 36.211 V8.3.0 [2008-05] 6.8, Physical downlink control channel, 3GPP TS 36.212 V8.3.0 [2008-05] 5.3.3, Downlink control information, and 3GPP TS 36.213 V8.3.0 [2008-05] 7, Physical downlink shared channel related procedures).
A terminal receives the PDCCHs and detects the assignment information of information transmission channels PDSCH of the terminal based on the PDCCHs for the terminal. The terminal then receives the PDSCHs based on the PDSCH assignment information. The PDCCHs are scrambled in different ways for the respective terminals. Each terminal decodes the PDCCHs using a unique decoding method and determines a correctly detected PDCCH as the PDCCH for the terminal. This processing is called blind determination.
As the control channel transmission method, control information for a Rel-8 LTE terminal and that for a broadband terminal may be transmitted using different resources. However, this resource use method cannot be efficient because the terminal existence ratio dynamically changes, as described above.
For this reason, there is a demand for development of a system which allows a Rel-8 LTE terminal (broadband reception apparatus) to receive PDCCHs without changing its specifications and an LTE-A terminal (narrowband reception apparatus) to efficiently receive PDCCHs.